This application claims the priority of Korean Patent Application No. 2003-87984, filed on Dec. 5, 2003, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to a flat panel display, and more particularly, to a flat panel display capable of selectively displaying two-dimensional (2D) and three-dimensional (3D) images.
2. Description of the Related Art
In general, a 3D image can be implemented using a viewer's binocular disparity. With the 3D image implementing method using the binocular disparity, there is a method where a viewer wears glasses for displaying the 3D image such as polarization glasses or liquid crystal (LC) shutter glasses, and a method where the viewer observes in his/her naked eyes using a unit having a lenticular lens, a parallax barrier, a parallax illumination or the like. The former method is called “stereoscopy method” and the latter is called “autostereoscopy method”.
The stereoscopy method is applied to a place where several persons can view an image using a polarization projector, such as a theater. Additionally, the autostereoscopy method can be applied to a game display, a home television set, an exhibition display and the like, which is used by a single person or a small number of people.
A current study is concentrated on the autostereoscopy method for implementing the 3D image, and several products relating to this are on sale.
3D-image display devices which are being currently introduced can implement only the 3D image, and are available at a higher price than a 2D-image display device.
However, since 3D image contents are not actively supplied, the high-priced 3D-image display device cannot satisfy customers' interest.
Accordingly, recent study has been made on a method for manufacturing a display device for selectively implementing the 2D and 3D images, and various products are being introduced.
Among the introduced products, there is a display for selectively displaying the 2D and 3D images using a liquid crystal shutter provided at a rear of a Thin Film Transistor Liquid Crystal Display (TFT-LCD). The display has excellent 2D/3D-image variable characteristics. However, due to a thickness of the liquid crystal shutter, the display is increased in thickness. Further, since the display uses a polarizer film, it is difficult to achieve light efficiency as desired.
FIG. 1 illustrates a conventional 3D-image exclusive flat panel display employing a parallax illumination way.
Referring to FIG. 1, the conventional 3D-image exclusive display includes a general Liquid Crystal Display (LCD) 10 for displaying an image thereon, and a slit plate 14 installed at a rear of a general LCD 10. The slit plate 14 is spaced apart from the LCD 10 by a predetermined distance (dS). A plurality of slits 16 are provided on a surface of the slit plate 14 facing LCD 10. Light incident on the slit plate 14 is incident on the LCD 10 through the slit 16. Accordingly, the slit 16 is a rod source for the LCD 10. In FIG. 1, a reference numeral 12 represents pixels of the LCD 10.
The 3D-image exclusive display shown in FIG. 1 has an advantage in that the structure is simple, and luminance is not only excellent, but also Moire interference is reduced in comparison to the display employing the parallax barrier method.
However, since the 3D-image exclusive display shown in FIG. 1 employs a fixed 3D method using a fixed slit plate 16, the viewer can view only the 3D image in which left and right images are separated. For all that, as described above, since 3D contents are infrequently supplied at present, and it is expected that the 2D and 3D contents will coexist for the foreseeable future, it is not easy for a customer to willingly purchase the high-priced 3D-image exclusive display.
Accordingly, a display for selectively displaying the 2D image and the 3D image (hereinafter referred to as “2D/3D display”) is required.
FIG. 2 illustrates a conventional 2D/3D display. In FIG. 2, a reference numeral A1 represents a liquid crystal panel for displaying the image thereon using a thin film transistor (“TFT”) as a switch element.
Referring to FIG. 2, a liquid crystal shutter A2 is provided at a rear of the liquid crystal panel A1, and a light source A3 is provided at a rear of the liquid crystal shutter A2. The light source A3 is a backlight used for the general LCD A1. An operation principle of the liquid crystal shutter A2 is identical with that of the liquid crystal panel A1. Accordingly, an electric signal applied to the liquid crystal shutter A2 is controlled to allow a specific region of the liquid crystal shutter A2 to function as a transmission region through which an incident light from the light source A3 passes, or to function as a shading region by which the incident light is shaded. Further, the electric signal applied to the liquid crystal shutter A2 is controlled to allow a region of the liquid crystal shutter A2 corresponding to the slit 16 of the display shown in FIG. 1 to function as the transmission region, and to allow a remaining region of the liquid crystal shutter A2 to function as the shading region. In case that the liquid crystal shutter A2 is driven as above, the 2D/3D display shown in FIG. 2 becomes identical with the 3D-image exclusive display shown in FIG. 1.
The electric signal applied to the liquid crystal shutter A2 is controlled to allow an entire region of the liquid crystal shutter A2 to function as the transmission region. In this case, the 2D/3D display shown in FIG. 2 becomes identical with a 2D-image display.
As such, the conventional 2D/3D display shown in FIG. 2 has an advantage in that since the liquid crystal shutter A2 can be used to selectively implement a 2D-image exclusive light source and a 3D-image exclusive light source, the 2D or 3D image can be selectively embodied.
However, the 2D/3D display shown in FIG. 2 has disadvantages in that the display can be increased in thickness and its manufacture cost can be also increased due to the liquid crystal shutter A2 provided between the liquid crystal panel A1 for displaying the image thereon and the light source A3, and further the light efficiency is reduced due to the necessity of inserting an additional polarizer film.
An observation distance (Lo) necessary for observing the 3D image is given in the following Equation 1.Lo=(d×E)/p  Equation 1
In Equation 1, “Lo” represents a distance from an image surface of the liquid crystal panel A1 to viewer's eyes 26L and 26R, and “d” represents a distance from a surface of the liquid crystal shutter A2 to the image surface of the liquid crystal panel A1. Additionally, “E” represents a distance between viewer's left eye 26L and right eye 26R, and “p” represents a pixel pitch of the liquid crystal panel A1.
Generally, the pixel pitch (p) of the liquid crystal panel A1 is about 110 μm, and the distance (E) between both eyes 26L and 26R is about 65 mm. Additionally, considering that a rear glass plate of the liquid crystal panel A1 has a thickness of about 0.7 mm, a polarizer has a thickness of 0.2 mm, and the glass plate of the liquid crystal shutter A2 has the thickness of 0.7 mm, the distance (d) is calculated as 1.6 mm. This distance (d) should be converted into air thickness since the image reaches the viewer through air. For this, the distance 1.6 mm is divided by 1.52. If these values are applied to the Equation 1, the observation distance (Lo) necessary for observing the 3D image is about 622 mm {[((0.7 mm+0.2 mm+0.7 mm)/1.52)*65 mm]/0.11 mm}.
Referring to FIG. 3, the liquid crystal panel A1 includes a first polarizer 50, a first transparent substrate 52, a first Indium-Tin-Oxide (ITO) electrode 54 connected to the TFT, a first liquid crystal layer 56, a second ITO electrode 58 used as a common electrode, a second transparent substrate 60 and a 135° polarizer 62, which are arrayed in a sequence from left to right as shown in FIG. 3. Additionally, the liquid crystal shutter A2 includes a third transparent substrate 70, a third ITO electrode 72 connected to the TFT, a liquid crystal layer 74, a fourth ITO electrode 76 used as the common electrode, a fourth transparent substrate 78 and a second polarizer 80, which are arrayed in a sequence from the liquid crystal panel A1 toward a light source A3. When the liquid crystal shutter A2 is in an on state, the incident light from the light source A3, that is, from the backlight, passes through the liquid crystal shutter A2 as it is, and when the liquid crystal shutter A2 is in an off state, a polarization direction of the incident light is rotated by 90°.
Considering the case that a personal LCD monitor is used as the 2D/3D display, the observation distance (Lo) is too long for a person observing with hands placed on a keyboard. Further, it is advantageous that the observation distance (Lo) is small in case that the 2D/3D display is applied to a personal mobile terminal such as a hand phone or a Portable Digital Assistant (PDA). Accordingly, in this aspect, it is difficult that the 2D/3D display shown in FIG. 2 is applied to the personal LCD monitor or the personal mobile terminal. Naturally, this drawback can be also solved by overcoming a difficulty in process to use a much thinner glass plate or a polymer substrate. However, since the liquid crystal shutter A2 of the 2D/3D display shown in FIG. 2 necessarily requires the polarizer film, it is difficult to achieve the light efficiency as desired by use of this solution.
Reference numerals L and R of FIG. 2 represents pixels of the liquid crystal panel A1. An image of a slit light source 22a seen through the pixel (L) is incident only on the viewer's left eye 26L, and the image of the slit light source 22a seen through the pixel (R) is incident only on the viewer's right eye 26R. Accordingly, the viewer feels the binocular disparity for the slit light source 22a, and views the 3D image.
As the observation distance and the light efficiency for the 3D image have become important factors, various 2D/3D displays have been introduced for improving them. FIG. 4 illustrates one example.
The 2D/3D display shown in FIG. 4 sequentially includes a retarder A5 and a liquid crystal shutter A4 patterned between the liquid crystal panel A1 for displaying the image thereon and the light source A3 for the purpose of shortening the observation distance, and is a structure diagram of a model recently shown to the market by Sharp. The retarder A5 allows the incident light having the same polarization direction as a fast axis of itself or the incident light having the polarization direction angled by 90° with respect to the fast axis to pass as it is, while as allowing the incident light having the polarization direction angled by 45° with respect to the fast axis. The liquid crystal shutter A4 includes a fifth transparent substrate 90, a fifth ITO electrode 92, a third liquid crystal layer 94, a sixth ITO electrode 96, a sixth transparent substrate 98 and a third polarizer 100, which are arrayed in a sequence of the retarder A5 toward the light source 30.
The conventional 2D/3D display has an excellent selectivity of the 2D and 3D images, but due to the use of the liquid crystal shutter having the same construction as the liquid crystal panel, in effect two liquid crystal panels are used. Accordingly, the conventional 2D/3D display is increased in thickness and power consumption. Further, the conventional 2D/3D display has a drawback in that the light efficiency is reduced since the polarizer film is necessarily additionally used due to a transmission-adjusting unit using the adjustment of polarized light.